1. Field of the Invention
This invention relates to inhalation therapy devices, and more particularly, to the design and construction of a nebulizer device for producing an aerosol spray delivered via flow of gas at varying oxygen concentrations. 2. Prior Art
It has been determined that a number of respiratory ailments can be treated by the inhalation of an aerosol spray of finely divided particles of water or other liquid medicaments. Devices referred to generally as nebulizer devices have evolved which are designed to produce such an aerosol spray. Nebulizers introduce a stream of pressurized gas, usually oxygen, into a chamber which entrains liquid particles so as to form the spray. Examples of these devices are shown in U.S. Pat. Nos. 3,652,015; 3,836,079; 3,915,386; and 4,036,919. The nebulizers shown in these patents are designed to operate with oxygen as the gas used to form the aerosol spray. This is because pressurized oxygen is usually available in each hospital room or at least in certain rooms. Care had to be exercised both in the design of the nebulizer and its operation as different patient conditions require different amounts of oxygen. The nebulizer devices of the prior art have been designed such that the lowest oxygen concentrations delivered to the patient were approximately 35% oxygen.
However, under certain conditions, it is believed beneficial if the oxygen is diluted with air such that the volume percent of oxygen being delivered to the patient approaches as much as possible the amount of oxygen in air--approximately 21%. To achieve lower oxygen concentrations, expensive regulators or blending equipment had to be used in combination with the nebulizer so as to reduce the oxygen concentration delivered to the patient to below 35%.
Another problem associated with some prior art nebulizers was in the fastening systems used to join the nebulizer to an associated bottle containing the liquid. This is especially important when the bottle is prefilled with a sterilized liquid. In the past, some fastening systems used an externally formed return tube provided on the nebulizer such that liquid which was not entrained by the gas and carried out of the nebulizer could be returned to the associated bottle. This not only required special construction of the nebulizer, but of the bottle as well. Further, such construction prevents a sterile field from being maintained, as during attachment of the nebulizer to the bottle, a separate puncture site had to be made in the bottle. Other nebulizers used a bottle having a very wide mouth such that liquid could be removed from and returned to the bottle through the mouth. Again, sterility of the liquid in such a case is difficult to maintain.
Finally, the prior art nebulizer devices generally required an aerosol-producing system which included an impaction post used to break up the liquid into fine droplets. The post had to be specifically located in order to insure that fine droplets were formed.
The present invention provides answers to these as well as other problems associated with prior art devices. In addition, the present invention provides such answers in a relatively straightforward manner enabling the device of the present invention to be easily manufactured and at a relatively low cost.